NASA's planet hunter, the Kepler space telescope. Image Credit/NASA
NASA’s Kepler space telescope has made major new strides in the search for extrasolar planets, producing its first candidates for Earth-sized worlds and the first worlds orbiting within what’s considered the habitable zones of stars, astronomers announced Wednesday.
The latest findings,, from the $600 million Kepler mission launched in March 2009, also include the discovery of another star with six planets, the most detected so far in another solar system.
The findings will require months to verify, astronomers advised but they are credible enough to merit publication in the Feb. 3 edition of the British science journal Nature.
“This is an amazing era of discovery in astronomy. But for exo-planets in particular there is no doubt the search for planets is motivated by a search for life,” said Debra Fischer, a Yale University astronomer who has monitored Kepler’s progress but was not part of the science team. “Humans are interested in whether life evolved on other planets, and we would especialy like to find communicating, high technology life. Naturally, we think that finding another Earth-like planet is friendly to the evolution of life.”
519 Previous Discoveries
Prior to Wednesday’s announcements, astronomers counted 519 planets circling other stars. Most were discovered using techniques different than those employed by Kepler.
Using a sensitive telescope to measure subtle changes in the brightness of other stars, Kepler detects a drop in the illumination as a planet crosses or “transits” the face of a star.
Just last month, Kepler scientists announced the discovery of the first rocky planet orbiting another star, a world about 1.4 times the size of the Earth but with an iron-like density.
Most of the previously discovered extrasolar planets relied on the detection of small wobbles in the central star that enterprising astronomers attribute to a gravitational interplay with an alien world. Most of the discoveries made since the first of those in 1995 were of Jupiter class exo-planets that circle their stars so closely they would be far too hot to support a water ocean where life might gain a foothold.
Habitable Zones Crucial
Kepler’s three to four-year mission is all about searching for sun-like stars with planets that resemble the Earth while orbiting in a “habitable zone.” The region is construed as being not too close and not too far from a star — just the right distance where the temperatures would support the presence of liquid water — one of the pre-requisites for life as we know it.
Kepler, which circles the sun on an Earth trailing course, observes a small patch of the Milky Way galaxy. The region, in the constellations Cygnus and Lyra, includes about 155,000 stars, most resembling the sun.
NASA’s William Boruki, who serves as the Kepler mission’s principal investigator, provided a breakdown of new findings made with the telescope between May 12 and Sept. 17, 2009.
New Exo-planet Candidates Exceed 1,200
They include 1,235 new planet candidates, more than twice the number detected using the “wobble” technique.
The total includes 68 that are “Earth-sized;” 288 that are considered “Super Earth’s” because they are about 1.4 times larger; 662 that are the size of Neptune; 165 that rival Jupiter in girth and 19 that are much larger.
Fifty four of the candidates reside in habitable zones. Of those, five are Earth-sized.
“The fact that we’ve found so manay planet candidates in such a tiny fraction of the sky suggests that there are countless planets orbiting sun-like stars in our galaxy,” said Borucki. “We went from zero to 68 Earth-sized candidates and zero to 54 candidates in the habitable zones, some of which could have moons with liquid water.”
Kepler’s latest findings hold even more intrigue.
Findings Include Alien Solar Systems
The telescope spotted 170 stars with more than one planetary candidate.
Kepler-11, one of the stars about 2,000 light years from the Earth, shows evidence for six planets. All Kepler-11 planets orbit their star within the same distance that Venus circles the sun.
All of the Kepler-11 worlds are larger than the Earth. The largest rivals Uranus in size.
“These six planets are mixtures of rock and gases, possibly including water,” said Jack Lissauer, a Keppler co-investigator. “The rocky material accounts for most of the planet’s mass, while the gas takes up most of the volume. By measuring the sizes and masses of the five inner planets, we determined they are among the lowest mass confirmed planets beyond our solar system.”
So, what would these planets look like up close? Nothing very familiar.
“Their density, is low and fluffy and sort of like marshmellow,” said Lissauer. “Maybe a marshmellow with a little hard candy at the core”